The present invention relates to an extrusion molding process, and more particularly to such an extrusion molding process in which the extruded tubular molding from an extruding die is clamped by two clamping devices at different elevations and downwardly stretched, and two symmetrical halves of a molding die are closed on the clamped molding between the clamping devices, causing the clamped molding to be compressed and molded into a finished product.
According to a conventional method of fabricating hollow plastic products through an extrusion molding process, plastic material is extruded into a molding through an extruding die and then seized by a clamping means and retained in a die cavity of a molding die, and then a cutting tool is moved to cut off the molding from the extruding die, and then a nozzle is inserted into the molding and air is blown into the molding in the die cavity of the molding die, causing the molding to be expanded and molded into a finished product. After molding, the molding die is lowered and then opened. After the finished product is removed from the molding die, the molding die is returned to its former position for a next molding cycle. This extrusion molding method has numerous drawbacks as hereinafter outlined.
1. Nozzle and blower means must be provided so that air can be blown into the extruded molding, causing it to expand in the die cavity of the molding die. PA1 2. When thermoplastic material is used and extruded into a molding through the extruding die and the extruded molding is seized by clamping means, the nozzle must be immediately inserted into the extruded molding so that the extruded molding can be swollen with to prevent its two opposite side walls from adhering together. This blow molding procedure is not suitable for making a hollow product having a short pitch between its two opposite side walls. PA1 3. If the peripheral wall thickness of the extruded molding is not uniform, the extruded molding will bias from its course, thus being unable to fall to the accurate position for catching by clamping means. Even if the extruded molding is seized by clamping means and put in the die cavity of the molding die for molding, the nonuniform wall thickness may cause the side walls of the finished product to be partially adhered together after the finished product is removed from the molding die.